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Re: Type of 'os' in gnu/system.scm
From: |
Saku Laesvuori |
Subject: |
Re: Type of 'os' in gnu/system.scm |
Date: |
Tue, 12 Dec 2023 09:44:20 +0200 |
> Hi,
>
> Looking at this definition in gnu/system.scm [1] I am trying to figure
> out what 'os' is:
>
> (define* (operating-system-kernel-arguments
> os root-device #:key (version %boot-parameters-version))
> "Return all the kernel arguments, including the ones not specified
> directly
> by the user. VERSION should match that of the target <boot-parameters>
> record
> object that will contain the kernel parameters."
> (append (bootable-kernel-arguments os root-device version)
> (operating-system-user-kernel-arguments os)))
>
> The same file also contains a record definition for <operating-system>
> so it seemed reasonable to assume that 'os' referred to such a
> record. In fact, the second procedure inside the 'append' above,
> operating-system-user-kernel-arguments, is one of the accessors [2]
> (even though the name does not match the field).
Yes, it is supposed to be an <operating-system> record (of course,
scheme does not enforce that in any way and it may end up being any
other type during runtime if there is a bug in some other code).
> In the first procedure bootable-kernel-arguments [3] however, 'os'
> (which is called 'system' there) is used like a string, although inside
> a gexp:
>
> (define* (bootable-kernel-arguments system root-device version)
> "Return a list of kernel arguments (gexps) to boot SYSTEM from
> ROOT-DEVICE.
> VERSION is the target version of the boot-parameters record."
> ;; If the version is newer than 0, we use the new style initrd parameter
> ;; names, otherwise we use the legacy ones. This is to maintain backward
> ;; compatibility when producing bootloader configurations for older
> ;; generations.
> (define version>0? (> version 0))
> (list (string-append (if version>0? "root=" "--root=")
> ;; Note: Always use the DCE format because that's
> what
> ;; (gnu build linux-boot) expects for the 'root'
> ;; kernel command-line option.
> (file-system-device->string root-device
> #:uuid-type 'dce))
> #~(string-append (if #$version>0? "gnu.system=" "--system=")
> #$system)
> #~(string-append (if #$version>0? "gnu.load=" "--load=")
> #$system "/boot")))
>
> I know objects in the store become paths when unquoted via '#$'. Does
> that also work for Guix records declared via define-record-type* [4]
> (please note the asterisk)? Thanks!
The <operating-system> record is expanded to a store path because there
is a (define-gexp-compiler ...) form for it in gnu/system.scm[1]. The
gexp expansion mechanism is explained quite well in a "Dissecting Guix"
blog post[2].
[1]: https://git.savannah.gnu.org/cgit/guix.git/tree/gnu/system.scm#n1623
[2]: https://guix.gnu.org/en/blog/2023/dissecting-guix-part-3-g-expressions/
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